DESCRIPTION: (Applicant's Abstract) Prenatal drug use is associated with a variety of medical and developmental consequences. Although many women spontaneously quit substance use on learning they are pregnant, others continue to use throughout pregnancy. Compared to alcohol and tobacco, little is known about prenatal quitting rates for illicit drug use. Also, little is known about the influence of alcohol and tobacco use on prenatal illicit drug use, and about psychological and other factors that account for the differences in ability of pregnant women to quit illicit drug use. Finally, better interventions are needed to enhance prenatal substance use quitting rates. Currently, the most common intervention is brief professional advice (BPA), which has only limited clinical effectiveness. To address these issues, a random-assignment clinical trial will be conducted to assess the effectiveness of two promising interventions of increasing clinical intensity on reducing prenatal opiate and/or cocaine use. Subjects will be pregnant women of lower socioeconomic status with less than a high school education (estimated gestational age at admission 20 weeks). Subjects with pre-pregnancy/prior prenatal opiate and/or cocaine use will be randomly assigned to one of three intervention groups (N=237/group): (1) BPA only (standard medical practice); (2) BPA in combination with behavioral incentives (BI); and (3) BPA in combination with BI and Motivational Enhancement Therapy (MET). Subjects will be followed prospectively throughout pregnancy and into the post partum period to determine changes that occur in substance use. Both self-report and objective measures of substance use will be employed. The study will also identify psychological and other factors (e.g., depression, maternal-infant interactions, drug use by significant other) that influence quitting and relapse to prenatal substance use. A comparison group of non-opiate/cocaine users (N=237) will be included to assess effects of prenatal opiate and/or cocaine use on maternal and infant outcomes. The study will also determine the influence of pre-pregnancy substance use on within-pregnancy quitting rates of illicit drug use, and the impact of quitting on maternal and infant health.